406 Edward Phelps Allis jr., 



was, according to Parker [57, p. 96], so named by Cuvier. Of 

 this Cuvierian postfrontal bone, in Salmo, Parker says that it "begins 

 as a delicate tract of osteoblasts, immediately outside the ampulla of 

 the anterior semicircular canal"; and he proposed for it the name 

 sphenotic. He considered it as a purely primary ossification, and it 

 certainly does not lodge in Salmo, as Schleip has shown for Salmo 

 fario and Salmo salar, and as I shall show for Salmo namaycush, 

 any part of the latero-sensory system. Later, Bridge [19] found, 

 in Amia, a small dermal bone overlying what he considered as the 

 "true sphenotic", and he called it the dermo-sphenotic in the text of 

 his work, and the dermo-postfrontal in the explanation of his plates. 

 Van Wijhe [78] adopted the prefix dermo-, thus introduced for 

 this bone by Bridge, and makes reference to a dermo-postfrontal in 

 Acipenser, as well as in Amia. I have described the corresponding 

 bone in Scomber [11], and have also called attention to its pro- 

 bable homologue in Gadus [4, p. 368J; usually using the name 

 postfrontal alone to designate the bone, but sometimes calling it the 

 dermo-postfrontal. In no other work that I can recall is a dermo- 

 postfrontal bone, as distinguished from the postfrontal bone of Parker's 

 interpretation of Cuvier's nomenclature, described in fishes, and the two 

 bones are usually assumed, or even definitely asserted to be inseparably 

 fused [63, 53]. And yet, so far as I can positively determine from existing 

 descriptions, this fusion of these two bones occurs, in the adult, or at 

 least occurs constantly, in Polypterus alone; for I have already stated 

 [2, p. 478] that the two bones were found easily separable in all the 

 many specimens of Amia that I have examined, and it will be shown 

 that the dermal canal element that is said by McMurrich [53] to fuse, 

 in Ameiurus, with the underlying sphenotic is either not a latero-sensory 

 bone at all, or not a latero sensory unit, and certainly not the homo- 

 logue of the dermal postfrontal of Amia. 



There are, in Amia, anterior, middle, and posterior head lines of 

 pit organs, and also a vertical cheek-line of similar organs, a horizontal 

 cheek-line, a mandibular line, and a gular line. The anterior head 

 line is a posterior continuation of the supraorbital canal line, and it 

 is innervated by a branch of the nerve that innervates that line. The 



